The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to an assembly of two concentric parts and a bearing between said parts for allowing a relative rotation between said parts around a vertical axis of rotation, wherein said bearing comprises an inner bearing ring, an outer bearing ring, axial rollers for transmitting, between the inner and outer bearing rings, axial loads in parallel to the vertical axis of rotation and radial rollers for transmitting, between the inner and outer bearing rings, radial loads in a direction towards or away from the vertical axis of rotation, wherein a first one of said bearing rings is attached to a first one of said concentric parts in a manner for maximally limiting a radial distortion thereof and wherein the second one of said concentric parts is connected to the second one of said bearing rings at an engagement location.
It is noted that in the present context the indication “radial distortion” means to express a rotation or deformation of a transverse cross section of a bearing ring (wherein a transverse cross section of a bearing ring is a cross section which is positioned in a vertical plane extending through the vertical axis of rotation). Such a radial distortion especially may be disadvantageous in a bearing when it occurs in only one of the bearing rings or in a different amount in both bearing rings.
Under ideal circumstances the load situation should be such that axial loads between the bearing rings extend through the axial rollers without causing a moment around said axial rollers, and such that radial loads between the bearing rings extend through the radial rollers without causing a moment around said radial rollers. Thus, in such ideal circumstances hardly any radial distortion between the bearing rings would be caused. However, circumstances in state of the art assemblies of the type referred to above are not that ideal. Because the second concentric part is connected to the second bearing ring at the engagement location, both axial loads and radial loads will be transmitted into the second bearing ring at and through said engagement location. Generally, in the state of the art, the engagement location is defined at the interface between the second concentric part and the second bearing ring, and will be offset both in a radial direction (towards or away from the axis of rotation) and in an axial direction (in a direction parallel to the axis of rotation) with respect to the axial rollers and radial rollers, respectively (meaning that the resultant of the axial loads transmitted at the engagement location does not extend through the axial rollers, but more inwardly or outwardly, and that the resultant of the radial loads transmitted at the engagement location does not extend through the radial rollers, but at a higher or lower level. Thus the resulting axial and radial loads transmitted at the engagement location may cause moments (around the axial and radial rollers), leading to stresses and (radial) distortions (especially of the second bearing ring). Such radial loads may for example be caused by horizontal accelerations acting on the second concentric part (which may have a substantial weight). The distortions may result in a relative rotation between the two cooperating bearing rings which only in a limited amount can be taken up by bearing clearances and which thus will result in an uneven loading of the rollers which can result in failure and/or accelerated wear of the bearing.